Double Debits on Account.

Dissapointed for doble deductions by FNB when I buy using debit card in shops. The bank deducted money on 27March 2021 and again on Sunday the 18th the same amount was deducted. Trying to get assistance but looks like no one is giving me a satisfactory answer and everday I receive a threatening message that my account is overdrawn and being charged again for something which is not of my making. Am very skeptical to contine buying using this debit card otherwise I will be charged double everytime. Evetime I confirm they will say in 24-48 hours the problem will be solved our technicians are working on it and the next another threatening message comes. I don't know how this is working. My first time to have such an experience. Evison